Electrical conductors are frequently terminated at their free ends with connection pieces which permit contacting of the conductor with corresponding contact partners. For this, inter alia connecting terminals are used which permit solder-free connection to the conductor structure. These terminals, which are also known as crimp connection terminals, are typically manufactured from a metal sheet by means of a punching process. In such case, a conductor-side section of the connecting terminal has at least one tab which is bent around the conductor and then is crimped therewith for the purposes of mechanical and/or electrical connection. In the case of electrical conductor structures which are coated with an insulating layer, such as a thin enamel layer or a parasitic oxide layer, the disturbing insulating layer must be removed or broken through to produce sufficient electrical contact between the connecting terminal and conductor structure. Connecting terminals in which the surface which contacts the conductor has special sharp-edged serration structures are used for this. Upon crimping of the connecting terminal, the parasitic insulating layer is broken through by the serration structures cutting into the metallic conductor. By means of appropriate crimping, good extension and associated galling of the materials involved is permitted, which in turn achieves good electrical contacting. The transition resistances prove to be stable long-term over the lifetime, in particular for aluminum conductors and hard copper conductors with small cross-sections.
The use of sharp-edged serrations, however, also leads to undesirable mechanical weakening of the relevant conductor, since the conductor cross-section is reduced at the relevant points by the serration structures cutting in. This effect proves particularly harmful in the case of conductors made from brittle materials, such as aluminum. Further, the use of such a connecting terminal may also be unfavorable in the case of conductors which are constructed from a plurality of thin strands. In this case, the sharp-edged serrations can cause severing of individual conductor strands.
A conventional connecting terminal is typically produced by means of a punching process, the serrations in a subsequent “ploughing” process being produced outside the punch. In this process, a plurality of knife-like “ploughing” structures arranged next to one another are drawn across the conductor contact surface of the connecting terminal transversely to the direction of insertion of the cable, to produce groove-like structures with symmetrical heapings of material.
Good electrical crimp performance in a stamped and formed terminal requires clean metal to metal contact between the terminal wire barrel and the wire strands. Serrations are typically stamped inside the wire barrel with the intention of generating sharp edges which can scrape through the oxides on the outside of the wire strands during the crimping process to produce these clean areas of metal to metal contact. Some terminals made from soft or thick materials can make it difficult to generate the desired sharp edges with only one hit of a serration punch since the soft and thick material simply pushes out of the way of the serration punch instead of flowing into the punch and taking on the intended shape.
It is, therefore, an object of the invention to provide an electric terminal which permits both sufficient electrical connection and sufficient mechanical connection between the connecting terminal and conductor and, in addition, is inexpensive to produce.